1. Field of the Invention
The current invention relates to a method for encoding a plurality of video signals into a single video signal, and in particular for encoding a plurality of video signals each representing a different view of the same scene into a single video signal.
2. Background Information
Three Dimensional (3D) autostereoscopic display apparatus allow multi-view 3D images to be observed without the need of wearing polarized or colored spectacles. Examples of autostereoscopic displays can be found in PCT patent publication WO 2007/059054 and US patent publications 2002/0011969, 2002/0036825 and 2007/0182738, the entire contents of which are incorporated herein by reference.
In order to integrate multi-view 3D video signals into existing video chains, the N-tiles format has been proposed and adopted in the autostereoscopic display systems mentioned above. In the N-tiles format each frame of video comprises N pictures of identical resolution, one from each channel. To be compatible with existing 2D video chains the N pictures are each compressed by downsampling so that all N pictures can fit into an equivalent 2D frame. The N-tile format is illustrated in FIG. 1. A plurality, in the illustrated case nine, video signals are generated by nine video cameras 1-9 each directed at a different view of the same scene 10. Each of the nine video signals, or channels, is downsampled by an N-tiles processor 11 and integrated into a single picture frame 12 by evenly distributing them in a 3×3 tile structure. In the illustrated embodiment with nine channels each signal is downsampled by three times along the horizontal and vertical directions so that its area is reduced by 1/9 of its original value. With this approach the multiple channels of video sequence will be encoded to an ordinary two dimensional video sequence enabling multi-view 3D images to be processed in identical ways as ordinary two dimensional (2D) video signal, and fit into existing video chains. At the receiving end the aggregated signals will be decoded back to the multiple video sequences, and display on the Autostereoscopic monitor through a process known as “Interdigitation”. However, the resolution of each view is degraded significantly and is not in line with the current HDTV trend.
Because of the downsampling in each channel picture quality is heavily degraded in resolution. This leads to a general blurring of the pictures when they are displayed on the autostereoscopic monitors and artifacts become even more prominent in stationary or slowly varying scenes where viewers have sufficient time to study the details. Although interpolation techniques can be applied to attain a more pleasing visual quality the computational loading is heavily increased and detail information that is lost in the downsampling process is not recovered.